Quality-Improved GaN Epitaxial Layers Grown on Striped Patterned Sapphire Substrates Ablated by Femtosecond Laser

Yichao Xu,Xiaoyan Lin,Wenjuan Wu,Jun Zou,Bobo Yang,Wenbo Li,Mingming Shi

doi:10.3390/app8101842

Abstract

In this work, we propose a new approach to create striped patterned sapphire substrate (PSS) under the circumstance that grooved patterned sapphire substrate technology exhibits more potential to reduce dislocation density in GaN (gallium nitride) epilayers. The striped grooves of patterned sapphire substrate are ablated by femtosecond laser. After the process of metal-organic chemical vapor deposition (MOCVD) method, the c-plane GaN epitaxial layers grown on striped PSS have larger crystallite size, which brings much less crystal boundary. There is much less compressive stress between the GaN crystals which improves the smoothness and compactness of GaN epilayers. This result demonstrates a significant improvement in the crystallinity of the c-plane GaN epitaxial layers grown on striped PSS.

Highlights

The application of sapphire in manufacturing light emitting diodes (LEDs) has become increasingly popular in the LEDs market ascribe to the low fabrication cost
To improve the performance of the films grown on sapphire substrate, a lot of methods have been put forward, such as the use of buffer layers [3], epitaxial lateral over-growth (ELOG) technology [4], Bragg reflecting layers [5], photonic crystals [6,7], surface coarsening [8,9], and flip-chip technique [10], a more efficient solution provided by some researchers is using patterned sapphire substrate (PSS) [11,12]
We focus on the crystallinity of the c-plane GaN epitaxial layers grown on striped patterned sapphire substrates ablated by femtosecond laser

Summary

Introduction

The application of sapphire in manufacturing light emitting diodes (LEDs) has become increasingly popular in the LEDs market ascribe to the low fabrication cost. To improve the performance of the films grown on sapphire substrate, a lot of methods have been put forward, such as the use of buffer layers [3], epitaxial lateral over-growth (ELOG) technology [4], Bragg reflecting layers [5], photonic crystals [6,7], surface coarsening [8,9], and flip-chip technique [10], a more efficient solution provided by some researchers is using patterned sapphire substrate (PSS) [11,12] It includes grooved type [13], hemispherical type [14], conic type [15] and hexagonal type [16] PSS (patterned sapphire substrate).

Materials andand

The schematic diagram of GaN-based

Results and Discussion

Phonon FWHM

Conclusions